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See the License for the * 011// * specific language governing permissions and limitations under the License. * 012// *************************************************************************************************************************** 013package org.apache.juneau.http.header; 014 015import static org.apache.juneau.http.Constants.*; 016 017import java.util.function.*; 018 019import org.apache.juneau.http.*; 020import org.apache.juneau.http.annotation.*; 021import org.apache.juneau.internal.*; 022 023/** 024 * Represents a parsed <l>Accept-Language</l> HTTP request header. 025 * 026 * <p> 027 * List of acceptable human languages for response. 028 * 029 * <h5 class='figure'>Example</h5> 030 * <p class='bcode w800'> 031 * Accept-Language: en-US 032 * </p> 033 * 034 * <h5 class='topic'>RFC2616 Specification</h5> 035 * 036 * The Accept-Language request-header field is similar to Accept, but restricts the set of natural languages that are 037 * preferred as a response to the request. 038 * Language tags are defined in section 3.10. 039 * 040 * <p class='bcode w800'> 041 * Accept-Language = "Accept-Language" ":" 042 * 1#( language-range [ ";" "q" "=" qvalue ] ) 043 * language-range = ( ( 1*8ALPHA *( "-" 1*8ALPHA ) ) | "*" ) 044 * </p> 045 * 046 * <p> 047 * Each language-range MAY be given an associated quality value which represents an estimate of the user's preference 048 * for the languages specified by that range. 049 * The quality value defaults to "q=1". 050 * For example... 051 * <p class='bcode w800'> 052 * Accept-Language: da, en-gb;q=0.8, en;q=0.7 053 * </p> 054 * <p> 055 * ...would mean: "I prefer Danish, but will accept British English and other types of English." 056 * 057 * <p> 058 * A language-range matches a language-tag if it exactly equals the tag, or if it exactly equals a prefix of the tag 059 * such that the first tag character following the prefix is "-". 060 * 061 * <p> 062 * The special range "*", if present in the Accept-Language field, matches every tag not matched by any other range 063 * present in the Accept-Language field. 064 * 065 * <p> 066 * Note: This use of a prefix matching rule does not imply that language tags are assigned to languages in such a way 067 * that it is always true that if a user understands a language with a certain 068 * tag, then this user will also understand all languages with tags for which this tag is a prefix. 069 * The prefix rule simply allows the use of prefix tags if this is the case. 070 * 071 * <p> 072 * The language quality factor assigned to a language-tag by the Accept-Language field is the quality value of the 073 * longest language- range in the field that matches the language-tag. 074 * 075 * <p> 076 * If no language- range in the field matches the tag, the language quality factor assigned is 0. 077 * 078 * <p> 079 * If no Accept-Language header is present in the request, the server SHOULD assume that all languages are equally 080 * acceptable. 081 * 082 * <p> 083 * If an Accept-Language header is present, then all languages which are assigned a quality factor greater than 0 are 084 * acceptable. 085 * 086 * <p> 087 * It might be contrary to the privacy expectations of the user to send an Accept-Language header with the complete 088 * linguistic preferences of the user in every request. 089 * For a discussion of this issue, see section 15.1.4. 090 * 091 * <p> 092 * As intelligibility is highly dependent on the individual user, it is recommended that client applications make the 093 * choice of linguistic preference available to the user. 094 * If the choice is not made available, then the Accept-Language header field MUST NOT be given in the request. 095 * 096 * <p> 097 * Note: When making the choice of linguistic preference available to the user, we remind implementors of the fact that 098 * users are not familiar with the details of language matching as described above, and should provide appropriate 099 * guidance. 100 * As an example, users might assume that on selecting "en-gb", they will be served any kind of English document if 101 * British English is not available. 102 * A user agent might suggest in such a case to add "en" to get the best matching behavior. 103 * 104 * <ul class='seealso'> 105 * <li class='extlink'>{@doc ExtRFC2616} 106 * </ul> 107 */ 108@Header("Accept-Language") 109public class AcceptLanguage extends BasicStringRangeArrayHeader { 110 111 private static final long serialVersionUID = 1L; 112 113 private static final Cache<String,AcceptLanguage> CACHE = new Cache<>(NOCACHE, CACHE_MAX_SIZE); 114 115 /** 116 * Returns a parsed and cached header. 117 * 118 * @param value 119 * The header value. 120 * @return A cached {@link AcceptLanguage} object. 121 */ 122 public static AcceptLanguage of(String value) { 123 if (value == null) 124 return null; 125 AcceptLanguage x = CACHE.get(value); 126 if (x == null) 127 x = CACHE.put(value, new AcceptLanguage(value)); 128 return x; 129 } 130 131 /** 132 * Convenience creator. 133 * 134 * @param value 135 * The header value. 136 * <br>Can be any of the following: 137 * <ul> 138 * <li>{@link String} - Converted using {@link StringRanges#of(String)}. 139 * <li><c>StringRange[]</c> - Left as-is. 140 * <li>Anything else - Converted to <c>String</c> then parsed. 141 * </ul> 142 * @return A new {@link AcceptLanguage} object. 143 */ 144 public static AcceptLanguage of(Object value) { 145 return new AcceptLanguage(value); 146 } 147 148 /** 149 * Convenience creator using supplier. 150 * 151 * <p> 152 * Header value is re-evaluated on each call to {@link #getValue()}. 153 * 154 * @param value 155 * The header value supplier. 156 * <br>Can be any of the following: 157 * <ul> 158 * <li>{@link String} - Converted using {@link StringRanges#of(String)}. 159 * <li><c>StringRange[]</c> - Left as-is. 160 * <li>Anything else - Converted to <c>String</c> then parsed. 161 * </ul> 162 * @return A new {@link AcceptLanguage} object. 163 */ 164 public static AcceptLanguage of(Supplier<?> value) { 165 return new AcceptLanguage(value); 166 } 167 168 /** 169 * Constructor 170 * 171 * @param value 172 * The header value. 173 * <br>Can be any of the following: 174 * <ul> 175 * <li>{@link String} - Converted using {@link StringRanges#of(String)}. 176 * <li><c>StringRange[]</c> - Left as-is. 177 * <li>Anything else - Converted to <c>String</c> then parsed. 178 * <li>A {@link Supplier} of anything on this list. 179 * </ul> 180 */ 181 public AcceptLanguage(Object value) { 182 super("Accept-Language", value); 183 } 184 185 /** 186 * Constructor 187 * 188 * @param value 189 * The header value. 190 */ 191 public AcceptLanguage(String value) { 192 this((Object)value); 193 } 194}